Thermodynamics of Salt-Doped Block Copolymers

Abstract

We provide a perspective on the thermodynamics of salt-doped block copolymer electrolytes consisting of ion-conducting and inert blocks, taking poly(ethylene oxide)-b-polystyrene and lithium salts as an example. We focus on the origin for enhanced immiscibility between the constituent blocks upon addition of lithium salts and discuss issues from selected experiments and from our recent self-consistent field study.

Self‐Assembly of Poly(vinylpyridine‐b‐oligo(ethylene glycol) methyl ether methacrylate) Diblock Copolymers

“…The protonation of P2VP will increase the polarity of 2‐vinylpyridine monomer, which increases its effective repulsion with oligoethylene glycol monomer and enhances the immiscibility. This effect has been captured by Nakamura and Wang's theory . In their theory, the change of χ parameter due to the addition of charge can be expressed as: where is the shift of original χ due to the altered monomer identity from 2‐vinylpyridine to protonated 2‐vinylpyridine, and is degree of protonation.…”

“…Several theoretical approaches have been developed to predict the effects of ions and charge on block copolymer self‐assembly in the solid state. In the dilute limit where ion–ion interactions are weak, Nakamura and Wang predict that blending block copolymers with ions with highly differing solubilities in the different blocks will increase their segregation strength because of preferential counterion solubilization in one block . This increase in the effective χ affects both the order–disorder transition temperature (ODT) and the domain spacing and has been used to effectively explain the effects of salt doping into block copolymers such as PS‐PEO.…”

“…In the dilute limit where ion-ion interactions are weak, Nakamura and Wang predict that blending block copolymers with ions with highly differing solubilities in the different blocks will increase their segregation strength because of preferential counterion solubilization in one block. [26][27][28] This increase in the effective v affects both the order-disorder transition temperature (ODT) and the domain spacing 29 and has been used to effectively explain the effects of salt doping into block copolymers such as PS-PEO. In the limit of high ion concentration and strong interactions between ion pairs, Sing and Olvera de la Cruz have modified self-consistent field theory by incorporating charge correlation to calculate phase diagrams.…”

Inorganic‐Macroion‐Induced Formation of Bicontinuous Block Copolymer Nanocomposites with Enhanced Conductivity and Modulus

“…[20] As demonstrated by the simulation results of de la Cruz and co-workers,t he strong electrostatic cohesion of one block can change the phase diagram of block copolymers,g iving rise to new phases that are inaccessible from conventional uncharged block copolymers,i ncluding percolated phases. [1,22,23] However,p hase transitions induced by multi-charged ions,p articularly the formation of bicontinuous structures,h ave been rarely reported, although multi-charged ions are preferable for achieving as trong electrostatic cohesion. [1,22,23] However,p hase transitions induced by multi-charged ions,p articularly the formation of bicontinuous structures,h ave been rarely reported, although multi-charged ions are preferable for achieving as trong electrostatic cohesion.…”

Synergistic effects of ion pairs on the dielectric properties of diblock copolymer melts

“…20 In view of this fact and eqn (5), it is also conceivable that similar effects should occur in the case of polymer mixtures. 4 Although several theoretical predictions such as the nonlinear effective Flory-Huggins c parameter 23 and the salt-induced phase coexistence between the lamellar and disordered phases 24 have been investigated in recent experimental studies, our current results imply additional non-intuitive phenomena in polymer electrolytes. 1(b), which clearly illustrates the substantial disparity between the dielectric functions 3 r (r) for unlike and like charges.…”